The main components of a drive-train of a motor vehicle are a drive aggregate and a transmission. The transmission converts rotational speeds and torques and thereby transmits a traction force provided by the drive aggregate to a drive output of the drive-train. The present invention concerns a method for operating a drive-train of a hybrid vehicle whose drive aggregate comprises at least an electric machine and an internal combustion engine. Between the internal combustion engine and a drive output is connected an automated variable-speed transmission. The electric machine is coupled by a friction clutch to a shaft of the automated transmission.
In the automated transmission, shifts are carried out with interruption of the drive torque delivered from the drive aggregate to the drive output, namely in such manner that initially, in a first phase the drive torque delivered to the output is reduced, then, in a second phase the actual shift operation is carried out, and thereafter, in a third phase the drive torque at the output is built up again. The carrying out of the actual gearshift or gear change in the automated transmission is divided into several part-phases, namely a first part-phase in which the currently engaged gear of the gearshift to be carried out is disengaged, a second part-phase in which a transmission shaft of the automated transmission is synchronized, and a third part-phase in which once the transmission shaft concerned has been synchronized the target gear of the gearshift or gear change to be carried out is engaged.
In current practice the synchronization of the transmission shaft to be synchronized takes place by means of synchronizer rings. This can result in relatively long shifting times.
Method for operating a drive-train in accordance with the characteristics of the preamble of claim 1 are known from DE 10 2008 002 380 A1 and WO 98/40647 A1.